OFFSET
0,2
COMMENTS
Pentagonal analogy of A075088.
MATHEMATICA
k = 1; t = Table[0, {50}]; While[k < 500000001, a = PrimeOmega[k] + PrimeOmega[3 k - 1] - 1; If[ t[[a + 1]] == 0, t[[a + 1]] = k; Print[{k, a}]]; k++]; # (3 # - 1)/2 & /@ t
Join[{1}, Table[SelectFirst[{#, PrimeOmega[#]}&/@PolygonalNumber[5, Range[ 110000]], #[[2]]==n&], {n, 20}][[All, 1]]] (* The program generates the first 21 terms of the sequence. *) (* Harvey P. Dale, Dec 27 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Mar 04 2012
STATUS
approved